Issue 138 January 2002
WHAT GOOD IS IrD,Eh?
PART 1: CORDLESS PROTOCOL

byJeff Bachiochi

Start • Standards Make It Happen • IrPHY • The Range • UART To IrDA • IR Encoder/Decoder • Gimme More • Sources & PDF

Standards Make It Happen

I dislike having to attend most meetings, however, I do appreciate the need for them and the benefits that can come to pass. The Infrared Data Association, founded in 1993, has defined a set of protocols for the use of IR in the cordless transmission of data. A set of three mandatory protocols (and a growing list of optional protocols) make up the IrDA standard. The three protocols are link management (IrLMP), link access (IrLAP), and physical signaling layer (IrPHY).

IrPHY, the bottom layer protocol, describes the requirements of the physical cordless hardware. The IrLAP protocol layer is responsible for establishing a reliable connection and the structured transfer of data among devices. At the top, the IrLMP protocol supervises multiple channels of communications through the IrLAP and IrPHY. As part of the IrLMP, the Information Access Service (IAS) keeps track of the connected devices, available services, and link parameters.